KEY POINTS:
Fletcher Construction has unveiled models showing how Mt Eden Prison will look after it is transformed into a mega-jail.
In May, the builder won the $216 million tender to upgrade the substandard prison and now it has circulated pictures of architects' models to show the extent of the
changes.
The pictures, by architects Stephenson & Turner, appeared in Fletcher's Raw newsletter.
The plans show the extent of the development on the site of the 120-year-old stone prison, where some inmates still use buckets as toilets.
The Department of Corrections awarded Fletcher, New Zealand's largest building business, the contract to expand the prison and create better living and working conditions for inmates and staff.
The old prison is at the centre of the plans and is being preserved. One wing may be used as a museum or tourist attraction.
Fletcher said it would increase the number of cells.
"The new prison will not only provide facilities that meet modern standards but will also include some future-proofing for up to 570 more prisoners to be accommodated on the site if required in the future," a company statement said.
The Department of Corrections said work started in July when a Fletcher Construction team moved on to the site.
The first three months of work involved shifting facilities, installing building services and demolishing surplus buildings to allow construction work to start in October.
The builder said the job was challenging and unusual.
"The existing Mt Eden Prison and Auckland Central Remand Prison need to stay open throughout the construction period. One of this project's challenges will be working on a secure and operating prison site."
The new buildings have design features which are also practical.
"The new accommodation buildings will feature an innovative twin-skin cladding system, providing security and privacy while also letting daylight in and giving the appearance of commercial buildings," Fletcher said.
Environmental issues also feature in the new design.
"While the Green Star rating system doesn't yet apply to these types of buildings, the Department of Corrections will be adopting Green Star principles by including energy-efficient building designs and materials and operating fittings and systems.
"The original Mt Eden Prison buildings are more than 120 years old and are listed heritage areas. Preserving and continuing to use these buildings has been a key feature in the planning of the new prison.
"Once the new buildings are finished, the heritage building will be renovated and refurbished to modern office standards for staff and administration use."
One Fletcher boss leading the prison job is now finishing an 11-level luxury apartment development.
Project manager Michael Pearson would go to work at at the prison once he had finished the extensions to the Stamford Plaza hotel on Albert St, Fletcher said.
EXPANSION
New Zealand's four new prisons:
* Ngawha in Northland.
* Auckland Women's at Wiri.
* Spring Hill at Te Kauwhata.
* Otago Prison, near Milton.